Long-term settlement and bearing capacity of foundations adjacent to vertical excavation at various parameters of soil viscosity

Abstract

Introduction. When the underground part of a high-rise building interacts with the surrounding soil massif behind the excavation pit, a complex heterogeneous stress-strain state occurs, transforming in space and time — during construction and during the exploitation of the building. Special issues arise when the soil massif is heterogeneous and has rheological properties, and an additional load acts near the pit excavation at the same time. Materials and methods. For the problem of the stress strain statement of soil with a weight behind the enclosure of a pit with a depth h, taking into account the influence of a distributed load q = const with a width b = 2a at a distance c from the edge of the enclosing structure of the pit, the stress components were obtained using a solution based on the Ribier – Filon trigonometric series. To determine the settlement over time of the foundation near the pit, the A.Z. Ter-Martirosyan’s model was used. To describe shear deformations and the Kelvin – Foigt’s model was used to describe volume deformations, assuming that ε.z(t) = ε.v(t) + ε.γ(t), according to the Henky’s system of physical equations. Results. An analytical method has been developed for quantifying the settlement of soil bases and foundations of nearby buildings behind the pit over the time. The graphs of the settlement-time with double curvature, as well as the graph of the long-term stability of the base are obtained. Conclusions. The solutions obtained can be used to determine the long-term settlements and bearing capacity of the foundations of buildings and structures with rheological properties near the pits. The selected geomechanical model of the foundation (its geometric parameters, initial and boundary conditions), as well as the computational model of the soil (linear, nonlinear and rheological) and the type of physical equations (Hooke system or Henky system), significantly affect the type of the settlement-time curve (S–t), as well as the bearing capacity of the soils. Collaborative using of A.Z. Ter-Martirosyan’s rheological model and Kelvin – Foigt’s rheological model makes it possible to obtain settlement-time graphs with double curvature, as well as a graph of the long-term stability of the soil base.